Minimum feature sizes of semiconductor devices continue to shrink to enable increasing device densities. One method of achieving such high density patterning is to use thin photoresist films to mitigate problems such pattern collapse of high aspect-ratio resist features upon development. One possible solution to the problem involves using a high-resolution, high sensitivity and high etch durability fullerene resist. However, even though the aspect ratios produced by such resists may be as high as 5:1, the overall etch depth is limited significantly by the usable resist thickness.
A multilayer hard-mask stack can allow a further increase of the aspect ratio of the etched image. Such methods may use a thick amorphous carbon, deposited in vacuo by chemical vapor deposition, which is then coated with a thin-silicon rich layer. A thin photoresist film is then sufficient to pattern the silicon-rich layer; thus avoiding pattern collapse. The silicon-rich layer is in-turn used as a hard-mask to pattern the carbon, giving a high aspect ratio carbon pattern suitable for providing a mask for etching the silicon wafer. By alternating from silicon to carbon rich materials and vice versa optimization of the overall etch selectivities of various substrates can be accomplished.
In recent years, methanofullerene materials have been used in hard-mask formulations. For example, Frommhold et al., in International Patent Application No. WO1013/117908 A1, describe a hard-mask material comprising a methanofullerene and a cross-linker, However, there continues to be a demand for hard-mask materials that exhibit reduced swelling and comingling when in contact with resist solvents, increased carbon content, lower etching resistance, and higher thermal stability relative to previous formulations. These improvements are exhibited by the materials described herein.